The present invention relates to heat exchangers and the method of making the same, and more particularly, to heat exchangers of the type embodying outwardly projecting fins and the method of making the same.
Heat exchangers embodying fins formed from the outer surface material of tubular members have been heretofore known in the art, being disclosed, for example, in Richard W. Kritzer U.S. Pat. No. 3,202,212 and Joseph M. O'Connor U.S. Pat. No. 3,692,105, wherein, in the aforementioned Kritzer patent, the fins are formed in the form of spines formed from the outwardly projecting ribs on the tubular member; and in the aforementioned O'Connor patent, fins are formed by cutting our gouging them from such upwardly projecting ribs and the portion of the tubular member directly underlying the ribs, to thereby afford fins having elongated base portions projecting outwardly from the side wall of the tubular member, with spaced fins projecting outwardly from the outer longitudinal edges of the base portions.
Finned heat exchangers of the type such as that shown in the aforementioned Kritzer patent or the aforementioned O'Connor patent have often been made in substantial lengths, such as, for example, thirty, forty or fifty foot lengths. In such instances, it is normally necessary to support such heat exchangers at various intervals throughout their lengths, such as, for example, at six or eight foot intervals. Heretofore, this has meant that in order to afford relatively smooth, suitable supporting surfaces for engagement with the necessary supporting members, previously formed fins had to be removed at such intervals by suitable means, such as, for example, grinding, which required an additional, and completely separate operation after the complete forming of the heat exchanger. Such additional processes have proven detrimental to the widespread adoption and usage of such finned heat exchangers.
Also, in the manufacture of finned heat exchangers of the type disclosed in the aforementioned Kritzer patent and O'Connor patent, as well as in other patents such as, for example, Stephen F. Pasternak U.S. Pat. No. 3,886,639, Stephen F. Pasternak U.S. Pat. No. 3,901,312 and Joseph M. O'Connor U.S. Pat. No. 3,947,941, when it was desired to afford a heat exchanger having fin-free end portions for affording supporting member or connecting members, the common practice has been either to (1) form fins on a work-piece from one end thereof to a point at or beyond the desired length of the heat exchanger, then cut off the desired length of the heat exchanger and subsequently remove the fins on the desired intermediate portions and/or end portions of that length by suitable means, such as, for example, the aforementioned grinding; or (2) commence forming fins in inwardly spaced relation to the end of such a work-piece, form the fins for the desired length on the work-piece, and then sever the work-piece in outwardly spaced relation to such last formed fin, and then, if desired, remove fins from intermediate portions and/or reduce the size of the end portions of the work-piece by suitable means, such as, for example, grinding. Again, such method of forming finned heat exchangers require the use of grinding or other material-removing operations on the desired intermediate and/or end portions of the work-piece, which are additional to and completely separate from the fin-forming operations on the work-piece.
Additionally, in the manufacture of extended lengths of finned heat exchangers for use in steam cooling towers, which exchangers have openings therein are adapted to receive tubular steel piping inserts, difficulties are encountered because the finning process lengthens the exchanger thereby resulting in uneven heat exchange wall thickness about the steel piping inserts. Also, the separate process of removing by grinding the formed fins at predetermined intervals adds to the problem of uneven wall thickness about the piping insert. Accordingly, such problems have severely limited the adoption and usage of such finned heat exchangers.